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Re: likelyhood for these avian clades?
From: Christopher Taylor <email@example.com>
Subject: Re: likelyhood for these avian clades?
Date: Fri, 21 May 2004 10:09:54 +1200
_Steatornis_ and Trogonidae are also connected by a number of plumage
characters, such as rictal bristles at the base of the beak.
Mayr (2003) demonstrated from literature review that the inclusion of
Trogonidae in 'Coraciiformes' (more specifically with Alcediniformes) that
was (supposedly) found by DNA-DNA hybridisation has not been much supported
by later molecular studies. Morphologically, an alcediniform-trogonid
connection was supposed to be supported by:
- Columella and naso-frontal hinge in skull as above
- Feet syndactyl (third and fourth toe partly coalescent)
However, the second toe is also coalescent with the third for most of
its length in the Alcedinidae, while it is turned to point backwards in the
Trogonidae. Mayr argued that the great difference between these conditions
made a connection between the two families unlikely.
On the whole, a Trogonidae (feeding on the wing, partly frugivorous) +
_Steatornis_ (feeding on the wing, frugivorous) clade is worth keeping as a
possibility, but not yet definite. Such a relationship is interesting from
an ecological perspective, as the nocturnal Caprimulgiformes would then
twice given rise to diurnal descendants (Trogonidae and Apodiformes), both
of which retained the extreme aerial specialisations of their ancestors.
The pes is not syndactyl in Trogonidae, but rather heterodactyl, a condition
in which the inner (second) toe has been retroverted. It should also be
noted that trogons also are extensively insectivorous.
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